From ashes to answers: How Catalonia's forest rangers track the causes of wildfires

While the country is on vacation, forest rangers — known as Agents Rurals in Catalan — are among the busiest professionals during the summer. They are responsible for monitoring forests and determining the causes of wildfires.

In mid-June, just days before one of the biggest wildfires of the year broke out in Lleida, claiming two lives and burning 6,500 hectares, the head of the department, Antoni Mur, welcomed a team from Catalan News to their headquarters in Santa Perpètua de Mogoda.

"In Catalonia, 90% of wildfires are linked to human activity in some way, whether due to accidents, negligence, or deliberate actions," he explained. As it turned out, the leading hypothesis for the fire in Lleida points to agricultural machinery used for cereal harvesting.

In fact, negligence alone caused 35% of wildfires in Catalonia last year. "It worries us a lot. There’s still a long way to go, from raising public awareness to better controlling risky activities," Mur says. 

But if there is one cause that is particularly worrying and difficult to prevent, it’s intentional fires. 

"One in four are caused intentionally. This is the hardest to tackle because it’s difficult to identify and hold the perpetrators accountable, and investigations are complex," he explains. 

Despite these challenges, most wildfires in Catalonia are extinguished quickly. In fact, 90% burn less than one hectare. 

As of the interview on June 18, out of 138 wildfires recorded so far this year, 137 had affected less than one hectare.

"This is largely thanks to the network of volunteers across the region, who can respond quickly and usually put out fires in their early stages," Mur says. 

How the causes are determined

Once firefighters have extinguished a blaze, it’s the forest rangers’ job to assess the burned area and investigate the cause.

"Right now, only 14% of wildfires have an unknown cause. For the rest, we’re able to identify the specific origin," Mur explains. 

The process begins by narrowing down the area where the fire started. "We do this by analyzing weather conditions, the fire's start time, and its shape," he explains. 

"We then study the marks the fire leaves on vegetation to narrow down the origin," Mur explains.

Once they’ve identified the likely starting zone — usually around 300 to 400 square meters — they begin a thorough investigation.

"In that area, we carry out a very detailed search to try to find the exact ignition point and any evidence of human activity," Mur explains. 

Using testimonies from the first people to raise the alarm, forest rangers build an initial hypothesis.

"We refine the hypothesis as we gather more data during the investigation, until we are able to conclude it," Mur says. 

To learn more about Catalonia's wildfire strategy, listen to this episode of our podcast Filling the Sink.